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Blood Vessels Types of Blood Vessels _________- vessels that transport blood away from the heart Veins - _______________________ _______ - microscopic blood vessels that allow exchanges between blood and tissues Differences between arteries and veins Compared to veins, arteries ______________ Have more smooth muscle and elastic fibers ______________ Vessel Structure - General All vessels same basic structure 3 wall layers (or tunics) ___________(externa) - elastic and laminar fibers _______________ Tunica_________(intima) _____________ elastic fibers and smooth muscle fibers endothelium – non-stick layer _________________ internal elastic lamina Lumen - __________ Blood flow through tissues From the heart blood flows into Aorta ___________ Arterioles _________ Venules ____________ Superior/ Inferior Vena Cava Back to the heart Vessel Structure – Elastic Arteries Elastic (conducting) arteries Near heart _________ More elastic fiber, less smooth muscle Lose elasticity with aging Vessel Structure - Elastic Arteries Aorta and elastic arteries ______________________ _______________ Large arteries expand, absorb pressure wave then release it with elastic recoil - Windkessel effect Help to push blood along during diastole ______________________ ______________________ Vessel Structure – Muscular Arteries Muscular (distributing) arteries Deliver blood to organs ________________ _________ Less elastic fibers Vessel Structure - Arterioles Arterioles __________________ _____________ Composition varies depending on position - more muscle, less elasticity nearer heart Regulate flow from arteries to capillaries Flow = ΔP/R vary resistance by changing vessels size __________________ _______________ Vessel Structure - Capillaries Microcirculation connects arteries and veins ____________________ __________________ Higher the metabolic rate, more capillaries in tissue Muscle many caps (>600/mm2) Cartilage none Vessel Structure - Capillaries Allow exchange of nutrients and wastes between blood and tissue _____________________ Basal lamina - connective tissue Endothelial cells Structure/function Mechanisms of Exchange Diffusion - major method used to exchange substances such as O2, CO2, glucose, and amino acids Vesicular transport - endocytosis and exocytosis of lipid-insoluble molecules __________- involves filtration and reabsorption Veins Venules merge to form veins Have 3 distinct layers; thinner walled than arteries due to thin tunica interna and media _______________________ Varicose veins ______________________ Help for venous return Skeletal muscle pump ___________________ force blood back to heart valves prevent back flow Important Terms Blood Flow Blood pressure Resistance Blood Flow _________- is the amount of blood flowing through a tissue in a given period of time Velocity of blood flow is inversely related to the diameter of the blood vessel ____________________________________ ____________________________ Blood Pressure Force that the blood exerts against the walls of a blood vessels Factors affecting BP include cardiac output, blood volume, viscosity, resistance, and the elasticity of the arteries Peripheral Resistance Resistance to blood flow due to the force of friction between vessel wall and blood _____________affected by blood viscosity, vessel length and vessel radius Sources affecting Resistance Blood viscosity- how thick or thin the blood is. Measured by hematocrit. __________-longer the vessel, the greater the resistance, the greater the BP ___________-smaller the vessel the greater the resistance